Re: [PATCH 1/3] unbound-dhcp-leases-bridge : fix bug 12694 - DHCP hosts not reliably propagated to DNS

Sorry for interrupting this train of thought. Wouldn’t it be easier to use the tools available from dhcpd?

dhcpd seems to have a way execute commands. And I would guess this would be cleaner than "watching" a file.

There are three execute commands: on commit on release on expiry

and these could be used to launch the needed unbound bridge command.

Here is where I found this: https://jpmens.net/2011/07/06/execute-a-script-when-isc-dhcp-hands-out-a-new... https://jpmens.net/2011/07/06/execute-a-script-when-isc-dhcp-hands-out-a-new-lease/

And here is additional info: https://wiki.samba.org/index.php/Configure_DHCP_to_update_DNS_records https://wiki.samba.org/index.php/Configure_DHCP_to_update_DNS_records

(Search for "on commit" on this page)

Jon

On Mar 28, 2022, at 12:00 PM, Michael Tremer <michael.tremer@ipfire.org mailto:michael.tremer@ipfire.org> wrote:

Hello Anthony,

Thank you very much for submitting this patch and welcome to the list.

I understand that it is easier to track any changes in the directory, but I don’t quite understand why the logic had to be changed that the changes will be applied at the end only.

Is this just to avoid that multiple updates happen one after the other or what are you trying to achieve?

-Michael

...

On 22 Mar 2022, at 03:47, Anthony Heading <ajrh@ajrh.net mailto:ajrh@ajrh.net> wrote:

Switch from inotify watching individual files to monitoring the containing directories, as because dhcpd renames its leases file into a backup, monitoring the single inode does not work well. Additionally, python appears to have a bug with replacing expired inotify watches on single files.

---

unbound-dhcp-leases-bridge | 47 +++++++++++++++++++++++++------------- 1 file changed, 31 insertions(+), 16 deletions(-)

diff --git unbound-dhcp-leases-bridge unbound-dhcp-leases-bridge index a2df5f1..6e22066 100644 --- unbound-dhcp-leases-bridge +++ unbound-dhcp-leases-bridge @@ -72,6 +72,15 @@ class UnboundDHCPLeasesBridge(object): self.fix_leases_file = fix_leases_file self.hosts_file = hosts_file

• # base mask for a completed file change
  

• mask = inotify.constants.IN_CLOSE_WRITE | inotify.constants.IN_MOVED_TO
  

• # IN_MODIFY since dhcpd appends lease updates to an open file
  

• self.watches = {
  

•     self.leases_file: mask | inotify.constants.IN_MODIFY,
  

•     self.fix_leases_file: mask,
  

•     self.hosts_file: mask
  

• }
  

• self.unbound = UnboundConfigWriter(unbound_leases_file) self.running = False

@@ -80,36 +89,42 @@ class UnboundDHCPLeasesBridge(object): self.running = True

# Initial setup

• self.hosts = self.read_static_hosts()
  

• self.update_dhcp_leases()
  

• update_hosts = True
  

• update_leases = True
  

• i = inotify.adapters.Inotify()
  
  

• i = inotify.adapters.Inotify([
  

• 	self.leases_file,
  

• 	self.fix_leases_file,
  

• 	self.hosts_file,
  

• ])
  

• for f in self.watches:
  

• 	i.add_watch(os.path.dirname(f), self.watches[f])
  
  

  for event in i.event_gen(): # End if we are requested to terminate if not self.running: break

• 	# Make pending updates once inotify queue is empty
  if event is None:
  

• 		if update_hosts:
  

• 			self.hosts = self.read_static_hosts()
  

• 			update_hosts = False
  

• 		if update_leases:
  

• 			self.update_dhcp_leases()
  

• 			update_leases = False
  	continue
  
  header, type_names, watch_path, filename = event
  
  

• 	# Update leases after leases file has been modified
  

• 	if "IN_MODIFY" in type_names:
  

• 		# Reload hosts
  

• 		if watch_path == self.hosts_file:
  

• 			self.hosts = self.read_static_hosts()
  

• 	file = os.path.join(watch_path, filename)
  

• 	if not file in self.watches:
  

• 		continue
  

• 	log.debug("Inotify %s: %s", file, " ".join(type_names))
  
  

• 		self.update_dhcp_leases()
  

• 	update_leases = True
  
  

• 	# If the file is deleted, we re-add the watcher
  

• 	if "IN_IGNORED" in type_names:
  

• 		i.add_watch(watch_path)
  

• 	if file == self.hosts_file:
  

• 		update_hosts = True
  
  

  log.info http://log.info/("Unbound DHCP Leases Bridge terminated")

-- 2.34.1